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109 lines
2.9 KiB
109 lines
2.9 KiB
11 years ago
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#!/usr/bin/python
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import time
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import struct
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import logging
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import sys
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slow_xor = False
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imported = False
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BLOCK_SIZE = 16384
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def run_imports():
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global imported, slow_xor, salsa20, numpy
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if not imported:
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imported = True
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try:
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import numpy
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except ImportError:
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logging.error('can not import numpy, using SLOW XOR')
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logging.error('please install numpy if you use salsa20')
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slow_xor = True
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try:
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import salsa20
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except ImportError:
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logging.error('you have to install salsa20 before you use salsa20')
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sys.exit(1)
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def numpy_xor(a, b):
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if slow_xor:
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return py_xor_str(a, b)
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ab = numpy.frombuffer(a, dtype=numpy.byte)
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bb = numpy.frombuffer(b, dtype=numpy.byte)
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c = numpy.bitwise_xor(ab, bb)
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r = c.tostring()
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return r
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def py_xor_str(a, b):
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c = []
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for i in xrange(0, len(a)):
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c.append(chr(ord(a[i]) ^ ord(b[i])))
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return ''.join(c)
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class Salsa20Cipher(object):
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"""a salsa20 CTR implemetation, provides m2crypto like cipher API"""
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def __init__(self, alg, key, iv, op, key_as_bytes=0, d=None, salt=None,
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i=1, padding=1):
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run_imports()
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if alg != 'salsa20-ctr':
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raise Exception('unknown algorithm')
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self._key = key
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self._nonce = struct.unpack('<Q', iv)[0]
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self._pos = 0
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self._next_stream()
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def _next_stream(self):
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self._nonce &= 0xFFFFFFFFFFFFFFFF
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self._stream = salsa20.Salsa20_keystream(BLOCK_SIZE,
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struct.pack('<Q', self._nonce),
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self._key)
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self._nonce += 1
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def update(self, data):
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results = []
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while True:
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remain = BLOCK_SIZE - self._pos
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cur_data = data[:remain]
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cur_data_len = len(cur_data)
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cur_stream = self._stream[self._pos:self._pos + cur_data_len]
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self._pos = (self._pos + cur_data_len) % BLOCK_SIZE
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data = data[remain:]
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results.append(numpy_xor(cur_data, cur_stream))
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if not data:
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break
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self._next_stream()
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return ''.join(results)
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def test():
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from os import urandom
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import random
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rounds = 1 * 10
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plain = urandom(BLOCK_SIZE * rounds)
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cipher = Salsa20Cipher('salsa20-ctr', 'k' * 32, 'i' * 8, 1)
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decipher = Salsa20Cipher('salsa20-ctr', 'k' * 32, 'i' * 8, 1)
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results = []
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pos = 0
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print 'start'
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start = time.time()
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while pos < len(plain):
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l = random.randint(10000, 32768)
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c = cipher.update(plain[pos:pos + l])
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results.append(decipher.update(c))
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pos += l
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assert ''.join(results) == plain
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end = time.time()
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print BLOCK_SIZE * rounds / (end - start)
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if __name__ == '__main__':
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test()
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